target _blank option for insert file

The best way would be if the module does not render a hardcoded link in the template but makes use of l() function instead. But seems to be not implemented right now.

Meanwhile there is another way i you don't want to hack the module. I did the following to override it for "icon with link":

1.) Create a custom Module

2.) Implement hook_theme_registry_alter():

/**
 * Implements hook_theme_registry_alter().
 */
function text_feature_theme_registry_alter(&$theme_registry) {
  $path = drupal_get_path(
    'module',
    basename(__FILE__, '.module')
    ).'/insert-templates';
  if (isset($theme_registry['insert_icon_link'])) {
    $theme_registry['insert_icon_link']['template'] = $path.'/insert-icon-link';
    $theme_registry['insert_icon_link']['theme path'] = $path;
  }
}

3.) Copy the corresponding tpl.php file from the insert module to your module in a subdirectory called "insert-templates" and override it according to your needs.

The cleanest solution would be to create a subtheme of your admin theme, copy the Insert module templates you want to alter to the subtheme's templates folder and alter the HTML there. Nothing to be changed in the module's source code and no need for a separate module.